Organic Light Emitting Diode (OLED) is one of the hotspots in today's research field of flat panel displays. As compared with liquid crystal displays (LCD). OLED displays have advantages of low power consumption, low manufacturing cost, self-illumination, wide viewing angle, and fast response speed, etc. Nowadays. OLED displays have begun to replace the traditional LCD displays in the display field such as mobile phones, tablet computers, digital cameras.